Removal of CO2 and H2 S from natural gases

Abstract

CO 2 and, where relevant, H 2 S are removed from natural gases which contain CO 2 and may or may not contain H 2 S by a process in which the said natural gases are treated, in an absorption stage at from 40° to 100° C., with an aqueous absorption liquid containing from 20 to 70% by weight of methyldiethanolamine, the treated natural gases are taken off at the top of the absorption stage, the aqueous absorption liquid laden with CO 2 and, where relevant, H 2 S is taken off at the bottom of the absorption stage and then regenerated in one or more flash stages, and the regenerated absorption liquid is recycled to the absorption stage.

We claim: 
     
       1. A process for removing CO 2  and, where relevant, H 2  S from a natural gas which contains CO 2  and may or may not contain H 2  S, which comprises: (a) treating said natural gas in an absorption stage at from 40° to 100° C. and at a pressure of from 10 to 110 bar with an aqueous absorption liquid containing from 20 to 70% by weight of methyldiethanolamine by feeding in the natural gas at the bottom and the aqueous absorption liquid at the top of the absorption stage, CO 2  and, where it is present, H 2  S being washed out by a counter-current procedure;   (b) taking off the treated natural gas at the top of the absorption stage;   (c) taking off the aqueous absorption liquid laden with CO 2  and, where relevant, H 2  S at the bottom of the absorption stage;   (d) regenerating the laden aqueous absorption liquid without the use of a stripping column by flashing the liquid in one or more flash stages, letting down the pressure in the last flash stage, or in the single flash stage where only one such stage is employed, to about 1 to 3 bar; and   (e) recycling the regenerated absorption liquid to the absorption stage.   
     
     
       2. The process of claim 1, wherein CO 2  and, where relevant, H 2  S are removed from a natural gas containing higher hydrocarbons in addition to methane. 
     
     
       3. The process of claim 1, wherein two or more flash stages are used for regenerating the laden absorption agent, and the pressure of the latter is let down to not less than 5 bar in the first flash stage after the absorption stage. 
     
     
       4. The process of claim 1, wherein the absorption liquid contains from 30 to 65% by weight of methyldiethanolamine. 
     
     
       5. The process of claim 1, wherein the absorption liquid contains from 40 to 60% by weight of methyldiethanolamine.